Receiver for signaling.



R. A. FESSENDEN.

RECEIVER FOR SIGNALING. APPLICATION FILED APR. 1'1I 1904.

Patented Aug. 29, 1911.

entree STATES PATENT caries.

REGINALD. A. FESSENDEN, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TOTHE NATIONAL ELECTRIC SIGNALING COMPANY, OF .EITTSBURG, I'ENNSYLVANIA,

A CORPORATION OF NEW JERSEY.

RECEIVER FOR SIGNALING.

Specification of Letters Patent.

Patented Aug. 29, 1911.

Application filed April 11, 1904. Serial No. 202,666.

have invented or discovered certain new and i useful lmprovemci'tts inReceivers for bigis a specification.

The invention described herein relates to certain improvements inreceivers for naling.

It is characteristic of most forms of coherers now in use, that they areformed of small irregular particles of conducting material so that, whenbrought into contact with each other, a surface of one particle may bein contact with a point of another particle: but, when decohered andagain brought into contact with each other, a sur face of one may bearupon a surface of the other. By reason of this variation in the areas ofcontact, the current passing through the cohcrer will vary, renderingthe signals received uncertain. Coherers have also been used in whichthe contacting surfaces are uniform, but the same surfaces are alwaysbrought into contact again after decohen ence. Vhcrc the samenon-conducting film is constantly acted on by the current, its characteris so changed as to cause variations in the voltage required to actuatethe coherer.

The non-conducting 'film referred to above and hereinafter as common toall forms of the apparatus described herein may be the oxidized skin ofthe metal or a thin film of fluid gas, such as air, or other well knownnon-conducting film such as oil, sulfid, etc., the action of which incoherers, particularly those of carbon, is well understood. lVithrespect to the contact between carbons Heaviside states in hisElectrical Papers, Vol. 1 page 183 as follows: There is or seems to be acushion of badly-conducting air between-two pieces of carbon in contact,which air is partially squeezed out by increasing the pressure, and theresistance .the clock work 4.

of carbon, or carbonized structured materequired. See alsolt-ighi-Dessau, Die Telegraphic ()lmc Dru/1.2%, section 36.

The object of the present invention is to insure uniformity of eachcontact electrical or physical as may exist or may be estabg lishedbetween the parts across a non-connaling, of which improvement thefollowing ducting film. and also the bringing of new surfaces intocontact.

The invention is hereinafter more fully described and claimed.

In the accompanying drawing forming a part of this specification Figure1 is a diagrammatic view illustrative of my improved receivingapparatus, and Fig. 2 illustrates a modified form of apparatus adaptedto prevent disturbing influences from affecting the indicatingmechanism, and Fig. 3 illustrates a further modification for thatpurpose. Fig. -it shows another modification of the apl iaratus.

In the practice of my invention parts or members 1 and 2 or 2 or 2" ofthe imperfect-contact receiver are so constructed that one shall have.movement relative to the other, so that the contacting surfaces can bechanged with sutlicient frequency to give operative uniformity.Convenient forms for these parts consist of a disk and asecond memberstationary relative to the directionof movement of the disk. The disk ismounted upon a spindle 3, which may be rotated by any convenient means,such as This disk may be formed rial, such as carbonized. velvet, ormetal such an. alloy of gold and bismuth, the latter forming of thealloy, or aluminum or mercury or osmium or iron. The other part ormember 2 ofthe coherer may be formed of carbon or metal. Both parts ormembers may be formed'of similar material. Vhen the part or member 1 isformed of carbon the part or member 2 is made by preference in the formof a roller mounted so as to bear upon the face of the disk and to berotated by contact therewith, as shown in Fig. 2. When using thisconstruction the disk is preferably constantly rotated by any suitablemechanism. As an indicating mechanism, a telephone 13 in the localcircuit, may be used. hen the part or member 2- is made in the form of apoint 2 as shown in Fig. 1, provision should be made for separatingthcfipai-ts or jmembers when one of them is shifted to change contactingsurfaces, to prevent the point from removing the non-conducting film andthus forming a constantly closed circuit.- A desirable constructionconsists in attaching the point 2 to a spring arm, 5, whereby the pointis held lightly in contact with the disk. small block of iron, (5, isconnected to the spring or point and serves as an arn'iature for theelectro-magnet, 7, which when energized will raise'the point clear ofthe disk. The rota.-

' tion of the disk is effected by the armature, 8, of the magnet througha pawl, 9, connected thereto and engaging a toothed wheel, 10, on thespindle. in order to preventthe point strikinghard-on the disk whenreleased, a thin light plate, 12, is secured to the spring to retard theaction of the latter. A clock work device l t 1S connected asthe circuitincluding the electro-magnet 7.

The signals may be read-from the relay or an indicating mechanism ordevice included in the circuit controlled by the relay or in thesecondarycircuit.

It is characteristic of my improvement that new surfaces are constantlybrought into contact with each other--the character, z'. 6., area, andshape of the surfaces in contact, being uniform and similar, so that foreach coherence the action is practically the same, and that anyinsensitive position of the contact does not persist on account of thefact that new surfaces are constantly presented. On account ofirregularities in the motion or ibration or surfaces, the contacts willnever be entirely uniform. Though I use a roller affording rolling oranti-friction bearing of the moving surfaces whereby new surfaces arebrought into contact with the least possible irregular variations in thecontinuity of a non-conducting film, and.

I though I also contemplate using a dead-surface such as carbon velvetor mercury, which tends to minimize or obviate vibration, neverthelessin order to eliminate residual effects when the above mentionedanti-vibratory surfaces are used, and also to en-' 'naling. Hence theindicating apparatus is v designed so as to respond only to impulseshaving a frequency equal to the number of electrical discharges persecond at the sendwhere 18 is a single telephone magnet and 19 ametallic tongue adapted to vibrate at the desired frequency.

As hereinbefore stated one of the contactlng surfaces may be formed of amaterial such as will give a yielding surface or a surface of a yieldingnature, by which is meant asurface capable of deformation by smallforces, such for example as the surface of mercury or a thin metal leaf.This form of receiver is especially useful in connection with indicatinginstruments having a variable zero, by whiclris meant, an indicatinginstrument in which the zero is not fixed, as in the case of a relay,but is variable, as in the case of a siphon recorder.

I am aware that imperfect contact devices have been constructed whereone or more of the contacts have been made movable for purposes ofadjustment, but the motion herein described does not refer to motion ofadjustment, which effects a change of sensltiveness by changing thepressure, but of motion for maintaining the sensltiveness practicallywithout changing and for retated preferably by a clockwork 4. The

conductor "may be a smallwheel so arranged that it is normally preservedfronn making contact with the mercury by the thin film 21 referred to inthe preamble which normally and inevitably covers a surface of mercuryexposed to air'. In lieu of the film of oxid other 'well knownequivalents in the art, such as films of oil, sulfid, etc, may be used,the action being identical in each case. The resistance of the film willdepend upon the degree of immersion or pressure. This was shown by\Vardsworth who calculated the thickness of films'of oil coveringmetallic surfaces by measuring the ohmic resistance of the films with asensitive 'galvanomcter and in general when ,one film is substituted foranother the same resistance may be obtained by suitably varying thethickness of the new film, for example the film formed on a coherer ofone of the common types may vary from, say one hum dred thousand ohms upto a value undetectable by the most sensitive galvanometer.

' has shown that a vacuum removes the thin fluid and yielding insulatingnon-conducting film of air on which the microphonic effects depends.

' tion I It will be 'understood that the contact defined herein is acontact across a non-conducting, insulating film, which should not bescraped off or have its continuity destroyed in the operation of theapparatus.

This application is a division or substitufor my co pending applicationNo. 125,032 filed September 27th, 1902, with an additional figure andsome elaboration of the description thereof as indicated in the originalspecification at page 3, lines 2 to 5 showing the disk as made ofmercury as there described.

I claim herein as my invention:

- 1. A receiver vfor wireless signaling having in combination two partsor members, one oi said members being of a yielding nature, meansfor-continuously changing the point of contacts of said members, and

means for selecting signals of a definite group frequency.

2. A receiver for wireless signaling, com prising a revolving disk andan electrode yieldingly' held in contact therewith, and means controlledby the action of the electro-magnetic waves for raising said secondelectrode 01? the disk.

REGINALD A. FESSENDEN.

Witnesses:

R. A. BALDERSON, A. M. BUNN.

